Our culture tends to minimize commitment.  If you make a promise or give your word and a better offer comes along everyone will understand, because that's what everyone does.  I've said it before, but God has called us to be different.  Sometimes we hesitate to make commitments because we aren't sure we can fulfill it.  That may be better than not honoring your word, but we need to be careful that our children and those around us see us making commitments and fulfilling them, especially when it is hard or inconvenient.  The lesson learned is to understand what we are committing to and take it as we would an oath.  Simply let your yes be yes, and your no be no.